Drug & supplement interaction

Calendula + Phenytoin

Phenytoin brand names: Dilantin Kapseals, Dilantin, Di-Phen, Dilantin Infatabs, Phenytek, and others.

Minor Interaction
Medically reviewed by · Updated September 2026
The bottom line Minor

Calendula has a minor interaction with Phenytoin. Theoretically, calendula might have additive effects when used with CNS depressants, although this appears to be unlikely.

Read the full interaction report
SeverityMinor
LikelihoodUnlikely
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Calendula and Phenytoin

Here is the interaction we found between these two, with the evidence behind it.

Minor

CNS DEPRESSANTS

Why this applies to Phenytoin

Phenytoin falls under CNS DEPRESSANTS — the group Calendula interacts with.

Theoretically, calendula might have additive effects when used with CNS depressants, although this appears to be unlikely.
Although some animal research has suggested that a saponoside constituent in calendula may have sedative effects, calendula has been used for over 30 years without reports of sedation in humans.
Severity Minor Likelihood Unlikely Evidence D

Interaction has been demonstrated in animal or in lab research but has been shown not to occur in humans..

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the short version: the concern with calendula and phenytoin is mostly theoretical. Animal studies hinted that one of calendula's plant compounds (a saponin) might cause mild sedation, so on paper it could add to the drowsiness phenytoin can already bring. But calendula has been used for over 30 years without anyone actually reporting this in people, so the real-world risk looks very low.

If you did somehow notice extra sleepiness, dizziness, or feeling foggy, that's worth mentioning. Most folks use calendula on the skin, where almost none gets into the body. Since phenytoin is a finicky drug to keep at the right level, it's still smart to run any new supplement past your pharmacist or doctor first.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Bojadjiev C. On the sedative and hypotensive effect of preparations from the plant Calendula officinalis. Nauch Trud Visshi Med Inst Sof 1964;43:15-20.
  2. Samochowiec L. Pharmacological study of saponosides from Aralia mandshurica Rupr. et Maxim and Calendula officinalis L. Herba Pol. 1983;29:151-155.
  3. Final Assessment report on Calendula officinalis L., flos. European Medicines Agency: Committee on Herbal Medicinal Products (HMPC). 2018. EMA/HMPC/603409/2017. Available at: https://www.ema.europa.eu/en/documents/herbal-report/final-assessment-report-cal

What These Ratings Mean

Every interaction above is graded three ways — here’s the key to each label.

Severity how clinically significant the interaction is
Major

Clinically significant. Avoid the combination, or use only under close professional supervision.

Moderate

Usually worth avoiding or managing — may need monitoring, a dose change, or timing apart.

Minor

Generally not serious. Be aware of it and mention it to your pharmacist.

Likelihood how strong the evidence is that the interaction actually happens in people
  • LikelyWell-controlled human studies have demonstrated the likely existence of this interaction.
  • ProbableInteraction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
  • PossibleInteraction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.
  • UnlikelyInteraction has been demonstrated in animal or in lab research but has been shown not to occur in humans.
Evidence the quality of the studies behind the rating (graded A–D)
  • AHigh-quality meta-analysis (quantitative systematic review).
  • BCase-control study.
  • CConsensus.
  • DAnecdotal evidence.

These ratings are for information only. Never start, stop, or otherwise change your therapy before speaking with your provider.

Keep it in perspective

Calendula Also Interacts With Other Medications

Calendula has 247 minor known drug interactions in our database — the Phenytoin one above is one of them. If you take anything else, check it against the full list below.

Minor 247 No known interaction 2,583 (incl. Phenytoin)
Taking anything else?

Check Another of Your Medications Against Calendula

Covers the 2,830 medications we’ve checked against Calendula. Pick one to open its full report.

From our Q&A

Questions About Calendula or Phenytoin

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Calendula or Phenytoin, not necessarily both, but if one is close to what you were about to ask it will usually go further than a database entry can:

Not quite your question? Ask our pharmacists directly — it is free, there is no account required, and answers usually come back within 24 hours.

Everything else you take

See Every Supplement That Interacts With Phenytoin

This page covers Calendula only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Phenytoin page lists 224 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: 1,4-butanediol (major), Activated Charcoal (major), Beer (major), Gamma-hydroxybutyrate (ghb) (major) and Kava (major).

By severity: 9 major · 187 moderate · 28 minor.

From our pharmacist’s overview on the Phenytoin page

“Phenytoin (Dilantin) is a seizure medicine with a narrow therapeutic index, meaning small changes in its blood level can bring seizures back or tip over into toxicity, so I treat its supplement list with real seriousness. The biggest group, 78 ingredients, piles on sedation, and alcohol, kava, and GHB all rate major for exactly that re…”

Reviewed by 2 · Jul 18, 2026

Open the Phenytoin interaction page

One more smart check

Taking Calendula as Part of a Dietary Supplement Product? Check It for Interactions

We hold 214 real supplement products containing Calendula, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Calendula. Your product may carry other ingredients that interact with Phenytoin too, on top of Calendula — and those would not show on this page. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Calendula and Phenytoin Sit Against Everything Else

Out of every supplement and medication people look up on HelloPharmacist, here is where these two land this week — and which way each has been moving.

Supplement Calendula
Steady interest

#1,030 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Phenytoin
Steady interest

#1,713 of 2,830 medications looked up here in the last 7 days

29 days ago today

Position among everything looked up on this site, not a measure of how commonly either one is used or how important it is. A supplement can climb this list because of a news story. It counts every request to the page, automated ones included, and nothing here identifies anyone.

Supplement

About Calendula

What is Calendula?

Calendula
  • Minor wounds and skin healing
  • Skin inflammation and irritation
  • Diaper rash
  • Mouth and throat inflammation
  • Soothing dry or chapped skin

Calendula is a flowering plant whose petals are used mainly in skin creams, oils, and ointments to soothe minor irritation and support wound healing. Some early research is promising for skin and mouth uses, but the overall evidence is limited. It is generally well tolerated on the skin, but people allergic to ragweed, daisies, or marigolds should be cautious.

Read the full Calendula monograph & all interactions
Medication

About Phenytoin

What Is Phenytoin Used For?

Brand names: Dilantin Kapseals, Dilantin, Di-Phen, Dilantin Infatabs, Phenytek, Dilantin injection

Phenytoin is used to treat and prevent seizures. The specific types covered depend on the formulation. Oral extended-release capsules (including Phenytek), chewable tablets (including Dilantin Infatabs and Phenytoin Infatabs), and oral suspension (including Dilantin-125) are used for tonic-clonic (grand mal) and psychomotor (temporal lobe) seizures; most oral forms also cover prevention and treatment of seizures occurring during or after neurosurgery. Chewable tablets and some capsule formulations also cover complex partial seizures.

Parenteral (injectable) phenytoin sodium is used for generalized tonic-clonic status epilepticus (a prolonged, life-threatening seizure emergency) and for prevention and treatment of seizures during neurosurgery. The IV form can also substitute short-term for oral phenytoin when a patient cannot take it by mouth.

See full Phenytoin drug information
Keep checking

Other Drugs & Calendula

Browse every other medication we’ve checked against Calendula — both the ones with a known interaction and the ones without. Select any drug for the full detail.

0Major
0Moderate
247Minor
2,582No known interaction
247 Minor 2,582 No interaction
Minor

247 interactions

Showing 60 of 247 minor interactions — see all 247 on the Calendula page.

No interaction 2,582 drugs checked — show the list

We also checked Calendula against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 2,582 medications checked with no known interaction — see the full Calendula list.

See the full Calendula interactions page
See every supplement checked against Phenytoin, ranked by severity
Sources

Sources & How We Checked

Interaction details are evidence-graded and sourced from the Natural Medicines database. The medication overview comes from MedlinePlus.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

Parts of this content are provided by the Therapeutic Research Center, LLC.

DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

© 2021 Therapeutic Research Center, LLC

Keep exploring
Calendula monograph › Uses, safety, and every drug interaction in one place Phenytoin supplement interactions › Every supplement checked against Phenytoin, ranked by severity Phenytoin drug information › The full plain-English guide to this medication Supplement interaction checker › Check any supplement or product against your medications Browse medications A–Z › Every drug we've checked against herbs & supplements Ask a pharmacist › Free, personal answer from our licensed team
Pharmacist Counseling Corner

Taking Calendula and Phenytoin Together: Common Questions

Can you take Calendula with Phenytoin?
There is only a minor interaction, which is usually not serious. Read the full details on this page and confirm with your pharmacist before combining them.
How serious is the Calendula and Phenytoin interaction?
We rate it Minor. This interaction is generally not clinically significant, but it remains worth noting and discussing with your pharmacist.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

Still Have a Question About Phenytoin and Calendula?

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This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.